Apple today announced the all-new Mac Pro will be available to order starting Thursday, December 19. Redesigned from the inside out, the all-new Mac Pro features the latest Intel Xeon processors, dual workstation-class GPUs, PCIe-based flash storage and ultra-fast ECC memory.

While it used the PCIe bus, if you plugged many of the standard PC components into the slots, they would not work. That's why companies like Sonnett Technologies made specific upgrade cards for Mac Pros. It's why ATI released "Mac Edition" upgrade video cards for use in Mac Pros.

Even the RAM was non-standard, requiring large heatsinks (so that Mac Pros, unlike their PC counterparts, would be quiet in operation). Again, aftermarket companies sprung into action producing Mac Pro specific DIMMS with compatible heatsinks.

Even replacement mechanical drive sleds, which only worked in Mac Pros, were produced by third party companies.

There were even external USB and Firewire hard drives produced with the same, distintive perforated aluminum chassis style to aesthetically match the Mac Pro.

How many upgrade components were available for the Mac Cube?

There were third party CPU upgrade cards, some with special ducting for cooling. There was a Geforce 2 MX video card in a version specially created for the Cube. The Cube used the same memory and hard drive components as a traditional desktop machine and these upgrades were common. And, unlike the Mac Pro line, the cube sold very poorly.

Upgrades for the new Mac Pro will be be plentiful. The RAM is standard, so that's a non-issue. The Thunderbolt 2 ports are an Intel standard and there are already PC motherboards with them. There are already Mac-specific Thunderbolt 2 to PCIe expansion chassis available, so you can add PCIe cards.

Apple has changed the upgrading game by going away from users shoving cards and drives into the box, a practice that resulted in an ungainly, huge box with a massively oversized cooling system and power supply. Now, a creative professional or engineer with a Mac Pro can have all of his mass storage on an external RAID interfaced by Thunderbolt 2 or USB 3.0. He can buy a new Mac Pro in a few years and swap it in with nothing more than moving a few external cables and a Time Machine restoration of the applications and settings from the RAID.